HOLT Electricians Practice Exam

When selecting feeder conductors, the highest rated motor should be based on what criteria?

1. Full-load current

2. Horsepower

3. Voltage rating

4. Torque rating

The correct answer is: Full-load current

When selecting feeder conductors for motors, the full-load current is the correct criterion to base the decision on. Full-load current refers to the maximum amount of current that the motor will draw when it is operating at its rated capacity. This value is crucial because it directly influences the conductor size needed to safely carry that current without overheating or causing voltage drop issues. Using full-load current ensures that the feeders can handle the electrical demands of the motor under normal operating conditions, providing both safety and efficiency. If the conductors are not appropriately sized based on full-load current, there can be serious risks of insulation failure or even fire hazards. While horsepower is a significant factor in determining the efficiency and performance of a motor, it does not provide the specific electrical characteristics needed for accurate conductor sizing. Voltage rating and torque rating are also important parameters in motor applications, but they do not directly correlate with the current that the feeder conductors must support during typical operation. Thus, focusing on full-load current is essential for safe and effective electrical design.